Study On The Spectral Characteristics Of The Common Organophosphorus Pesticides And Its Application

In this paper the absorption spectra and the three-dimensional fluorescence spectra ofthree organophosphorus pesticides, parathion parathion-methyl and isocarbophos in theirmethanol solution and ethanol solution are measured and their characteristics of theabsorption spectra and the fluorescence spectra are studied by using the FLS920Pmultifunction spectrometer. The mechanism of the spectra are analyzed from the resultsthrough obtained by optimization by quantum chemistry computing software. Thefluorescence spectra of three the organophosphorus pesticides in different time of UV-lightand different temperature are measured respectively and the reasons of their variation areanalyzed.The fluoresce characteristics parameters: the absorption range, the absorption peakwavelength, the absorbance, the effective excitation wavelength range, the best excitationwavelength, the fluorescence emission wavelength and the fluorescence emission peakwavelength are obtained. Results show that the absorption of them are strong in the UV-lightand the fluorescence can be obtained under the excitation of the UV-light. The absorptionpeak wavelength of the three pesticides in their methanol solution and ethanol solution are304nm/298nm,304nm/304nm and286nm/286nm respectively. The fluorescence emissionpeak wavelength of them are404nm/403nm,407nm/402nm and423nm/415nm. The spectracome from the n electron transition of S atom, the different in their spectra characteristicscome from the different type and location of the substituent group their fluoresce in differentsolutions accord with the law that the peak wavelength will red shift as the solvent polaritygrows.The molecular configuration of parathion and parathion-methyl are built by the quantumchemistry software GaussView5.0their ground configurations are optimized through thesemi-experience method AM1using the software Gaussian09w and then it is optimized to theexcited configuration by using the method CI-S. The absorption spectra of the groundconfiguration and the fluorescence emission spectra are computed by using the TD-DFT inthe level of B3LYP/6-31+G （d）. The computed value and the experimental value ofabsorption spectra of two pesticides in their methanol solution are277.23nm/304nm and276.21nm/304nm, that of the fluorescence spectra of the two pesticides in their methanolsolution are397.26nm/404nm and398.70nm/407nm. The results show that the configurationand the calculation method are reasonable. The main level jump producing the absorptionspectra from computing are7575（HOMO）â†'77（LUMO） in parathion and65（HOMO）â†'69（LUMO） in parathion-methyl. The fluorescence are produced while the n electrons of S atom produce delocalization after they are excited and then jump to the ground state throughthe Ï€₁^*â†'Ï€1radiation by comparing the optimized ground and excited configurationparameters.The stability of the three pesticides in different time of UV-light and differenttemperatures are stability by using the fluorescence spectra. The fluorescence spectra of thethree pesticides are obtained in different time of UV-light and different temperatures. Thestability is analyzed by comparing the spectra characteristics of the three pesticides.The research results provide new methods for the enrichment and development of thetype identification. And they also provide some theory support and help for the procedureinnovation and technical progress in the field of the organophosphorus pesticides supervision.